Does anybody know of instances where Ducati failed to number a frame? I ask because I just purchased a project bike, an 860 which has an engine number but supposedly no frame number. It also appears on Robert Miller's list in that way. I've emailed Robert.

Yes that's true. I have bought it from abroad so not had a chance to take a proper look. Will let you know when this has happened. Had some help meantime from Robert Miller who has provided some very useful info.